Field of the Invention and Related Art Statement
The present invention relates to a technique for detecting or measuring the condition of an engine oil, and more particularly to an apparatus for detecting the deterioration of the engine oil in an accurate and reliable manner. The present invention also relates to an apparatus for detecting the progress in the deterioration of the engine oil used in a motor car, while the apparatus is installed on the motor car.
Nowadays, the engine for the motor car has been developed to have high output power and excellent property, and thus the engine oil is liable to be used under severe conditions. Therefore, the deterioration of the engine oil has to be detected accurately and deteriorated engine oil has to be replaced with a new oil at a suitable time. To this end, the progress in the deterioration of the engine oil has to be detected accurately and undesired conditions such as the production of a large amount of sludges and the abrupt increase in the viscosity called oil thickening have to be avoided.
In general, the deterioration of the engine oil has been checked at a gas station in such a manner that an oil level gauge is pulled out of the engine and the dirtiness or blackening of a small amount of the engine oil adhered to a tip of the oil level gauge is visually checked and the viscosity of the engine oil is checked by fingers. However, such a known checking method is dependent on the experience of the human being, so that the degree of the deterioration of the engine oil could not be checked precisely. Particularly, the error due to the variation of respective operators could not be avoided.
In the Japanese Patent Application Laid-open Publication Kokai Sho 61-76938, there is described a known apparatus for detecting the deterioration of the engine oil. This known apparatus is based on the fact that the deterioration of the engine oil is related to the dirtiness of the engine oil. In this known apparatus, the engine oil whose dirtiness is to be detected is filled in a transparent vessel, a light beam having the visible wavelength is made incident upon the vessel, and the intensity of light transmitted through the vessel is detected to measure the dirtiness of the engine oil.
The above mentioned known apparatus can provide a measure for indicating the deterioration of the engine oil, because an amount of soots or carbon blacks and metal dusts introduced into the engine oil is increased in proportion to the time period during which the engine oil has been used. However, the inventors have found that the deterioration of the engine oil is not directly related to its dirtiness, but is mainly determined by the oxidation of the oil. Therefore, the known apparatus could not detect the true deterioration of the engine oil accurately, so that the engine oil could not be replaced at a suitable time on the basis of the detection result derived from the known apparatus.
The inventors have conducted various experiments and analyses and have found that the true deterioration of the engine oil is caused by the oxidation and the production of polymers due to the high operating temperature, so that the dirtiness could not indicate precisely the deterioration of the engine oil. For instance, although an amount of the soots and metal dusts introduced into the engine oil is small, the engine oil might be often deteriorated to a great extent due to the abrupt increase in the nitro oxidation under the high operating temperature. In such a case, there might be induced serious engine trouble by merely detecting the dirtiness of the engine oil. In this manner, the actual deterioration of the engine oil could not be measured only by detecting the dirtiness of the oil. The actual deterioration of the engine oil could be measured in the terms of total acid value, total base value, viscosity, etc. which is defined in ASTM. However, it is practically impossible to measure these parameters in a simple and reliable manner at the gas stations.
Furthermore, the above described known apparatus for detecting the dirtiness of the engine oil is constructed as a portable one and a small amount of the oil has to be sampled from the engine and is introduced into the apparatus. On the other hand, it is very convenient for drivers to indicate the deterioration of the engine oil during the actual running, so that the timing of replacing the engine oil could be determined correctly. Then, the engine oil could be exchanged at a suitable time, so that the running cost could be decreased, while the occurrence of the engine trouble due to the deterioration of the engine oil could be avoided.